Follow these four simple steps:
1. Calculate all your monthly debt payments. If you don't have fixed monthly payments, one way is to estimate your monthly payments as 4 percent of the total amount you owe.
2. Take your gross annual wages (total amount you make per year before taxes and other deductions come out) and divide them by 12 — that's your monthly income.
3. Take your monthly debt payments total and divide it by your monthly income.
4. Move the decimal point two digits to the right to make it a percentage — that's your debt/income ratio.